Knee Articular Cartilage Repair in Teen Athletes

Many different techniques have been developed to repair holes in the chondral (cartilage) surface of the knee joint. Studies have been limited to the results of these treatment approaches in adults. In this report, teens between the ages of 14 and 18 years of age are the focus.

Each of the 35 participants in the study had knee pain from a large (more than one centimeter-squared) defect in the osteochondral layer of the knee joint. "Osteo" refers to bone, whereas "chondral" directs our attention to cartilage. So the osteochondral layer is the cartilage next to the first layer of bone in the knee joint.

Defects in the osteochondral layer are fairly common in active adolescents. This type of problem usually develops as a result of trauma. Often there has been a direct blow to the knee. But minor trauma and repetitive motion with a shearing force can also contribute to the development of painful knee problems from osteochondral lesions.

Each patient was treated with a specific approach called autologous chondrocyte implantation or ACI. Autologous tells us the graft was taken from the patient him- or herself. A donor sample of chondrocytes comes from a non-weight-bearing section of the knee.

The cells are taken to a lab where they are grown into a larger donor patch of articular cartilage cells. This can take anywhere from four to six weeks. When there are enough lab-grown chondrocytes, the patient comes back in for part two of the surgical procedure.

In this operation, the damaged cartilage is cleaned out and the edges are shaved smooth in preparation for the graft material. The hole is filled in with donor chondrocytes and covered with a special membrane that is stitched in place, sealed, and watertight.

After a short post-operative period of immobilization (10 days), each patient went to Physical Therapy for a rehab program. Everyone followed the same program of leg exercises and activities (e.g., swimming, bicycling, rowing). The athletes were not allowed to participate in running or any impact sports.

Follow-up extended anywhere from one full year up to 10 years after the procedure. The results were measured based on pain, knee motion, and function. Tiny biopsy samples of the graft cartilage were also taken to look at the results at the cellular level (under a microscope).

A large number of the group (84 per cent) had excellent results regardless of the size of their lesion (large or small). Pain was less and both motion and function were improved. Of particular interest was the condition of the graft site later. Slightly more than half the group (57 per cent) had a patch of fibrous cartilage fill in the defect.

One-fourth of the group (about 24 per cent) formed the desired hyaline cartilage. A smaller number of patients (19 per cent) formed a mixture of fibers and hyaline cartilage. Only one patient had a failed result requiring additional surgery.

The authors took a look at some of the other factors to see if any of these affected the final result. For example, they noted that all but one patient had just a single (called isolated osteochondral lesion. But the lesions weren't all in the same spot of the knees.

There were some lesions located (14) on the medial side (side closest to the other knee) at the end of the femur (thigh bone where it joins to form the knee). Half that number (7) were located on the back of the patella. And another six were found on the lateral side of the femur (side away from the other knee). Results did not appear to be influenced by the location of the knee either.

Interestingly enough, results measured by pain, motion, and function weren't different (or less positive) when the repaired joint surface turned out to be just fibrous cartilage instead of the real thing. In other words, results were just as good when the repair tissue was not identical to normal hyaline cartilage covering the joint.

The researchers who conducted this study came to two basic conclusions. First, autologous chondrocyte implantation (ACI) works well in adolescents with painful osteochondrocyte lesions. This is true even when the final tissue isn't true hyaline cartilage.

And second, these results point to the need to try other types of cartilage repair (e.g., mosaicplasty, microfracture, abrasion techniques) and see how well they work with this age group. It's not clear if lesions that don't cause pain should be treated. But previous studies support the surgical treatment of painful defects before further joint degeneration occurs.

Reference: Simon Macmull, MBBS, MRCS (eng), et al. Autologous Chondrocyte Implantation in the Adolescent Knee. In The American Journal of Sports Medicine. August 2011. Vol. 39. No. 8. Pp. 1723-1730.

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